We have a lot of problems when using polymeric columns in the analysis of Oxytetracycline.
We use the method of European Pharmacopoeia and the column used is a PRP-1 (Hamilton)
If there is someone that is working with this kind of columns we'll be grateful about any suggestion.

Dear Ana,
Would you please go more detail about the problems. I do not know what is difference between USP and European methods. I used PRP-1 for oxytetracycline analysis followed USP method. I do not encount any problem. (resolution and taling factor are very good).

Ana,
You can check Hamilton website http://www.hamiltoncompany.com for oxytetracycline application note by USP method.
It is application #307.

The conditions for the PRP-1 column are listed below. THe retention times are about 7.5 minutes for Oxytetracycline and 15 minutes for tetracycline.

Oxytetracycline and Tetracycline by the USP Method on 250 x 4.1 mm PRP-1 (USP L21 Packing, P/N 79422)

Oxytetracycline 60 ppm
Tetracycline 120 ppm

Conditions: 50 gm t-Butyl Alcohol, 60 mL 0.33 M Phosphate buffer (pH 7.5), 50 mL 1% Tetrabutylammonium Hydrogen Sulfate, 10 mL 0.04% EDTA diluted to 1L with DI Water. Isocratic. 60°C
Flow: 1 mL/min.
Injection: 100 uL
Detection: UV at 254 nm

You can also get a copy of the chromatogram from the Hamilton web site or just send me a message with your e-mail address at hplc@hamiltoncomp.com

Mike Benning

For Sha.
Dear Sha
I'll try to explain my problems with Oxitetracycline.
At the beginin all is all right but after a few injections, the tail peak desappears and afther that the main peak has a big shoulder that includes the tail.
The chromatografic conditions are:
Mobile Phase: 60g t-butanol + 100 ml solution A + 50 ml solution B + 10 ml solution C to 1000 ml destilled water
Solution A: 2g K2HPO4 to 200 ml (pH = 8.0)
Solution B: 0.68 g tetra n-butilaminium hydrogen sulphate to 100 ml (pH = 9-9.5)
Solution C: EDTA 0.1M (pH = 8.0)
Vol. injection: 10 microliters
Temp. : 60 °C
Detection : 264 nm
Flow : 1 ml/min

Also:
Do you know the European Method, published in the Eur. Ph. 3ª Ed. We are working acording to this methodology because we need to quantify the impurity (4-epioxitetraciclyne).
Is it possible, with the US method, to determine the impurities of Oxitetraciclyne?

Thank you

I have found better luck using Polymer Labs PLRP-S column for tetracycline analysis. I've used this column successfully with either 0.1%TFA or 10 mM oxalic acid as mobile phase modifiers.